Rate-distortion optimal high-resolution differential quantisation for sinusoidal coding of audio and speech

Sinusoidal coding plays an important role in low-rate audio coding. Typically, (time/frequency) differential techniques are employed to reduce the bit rate for representing the sinusoidal components. In this paper we derive optimal entropy-constrained differential quantisers for quantising the sinusoid parameters. More specifically, the quantisers minimise a perceptually relevant distortion measure while the corresponding quantisation indices satisfy an entropy constraint. The quantisers turn out to be flexible and of low complexity. Subjective evaluations with audio signals suggest a bit-rate reduction as high as 20% with the derived quantisers over state-of-the-art (logarithmic) quantisers.